Method and means for controlling the tone of a radio set



Dec. 17, 1935. L WILLGING' 2,024,321

METHOD AND MEANS FOR CONTROLLING THE TONE OF A RADIO SET Filed March 25,1931 INVE N TOR.

A TTORNEYS Patented Dec. 17, 1935 UNITED STATES PATENT OFFICE METHOD ANDMEANS FOR CONTROLLING THE. TONE OF A RADIO SET Application March 23,1931, Serial. No. 524,419

4 Claims.

My invention is addressed to means for effecting so-called tone controlinradio sets; but it is an object of my invention to provide means and amethod for tone control which goes beyond the mere relative suppressionof undesired frequencies, and accentuates the desired frequency range.

It isan object of my invention to provide in a tone control means and amethod, when, for example, the treble range is desired, not only tosuppress the lower frequencies, but to reinforce and build up the volumeof the higher frequencies.

Conversely, it is my object when stronger bass values are desired, toprovide a means and method not only to suppress the higher frequencies,but also build up, reinforce, and strengthen the lower frequencies.

Consequently, it is my object to achieve in a tone control, adequate andfull range variation of tone, so called, without substantial change in 7volume.

It is a further object of my invention to provide a tone control whichis continuously variable from extreme treble to extreme bass.

These and the more specific objects of my in-, vention which will be setforth hereinafter, or will be apparent to one skilled in the art uponreading these specifications, I accomplish by that certain constructionand arrangement of parts of which I shall now describe a preferredembodiment, reference being had to the drawing in which I have shownonly so much of a radio circuit as is necessary to the comprehension ofmy invention.

My method is applied to the audio frequency portion of a radio receivingsystem, but is not restricted to any particular type of set or circuit.

In the practice of my invention I raise the tone, so called, byaccentuating the higher frequencies. This is accomplished byregeneration at the higher frequency, involving the feeding from thetreble position, resistance is introduced into.- the. feed back circuitin such a Way as ultimately to eliminate the said regeneration. Duringthe shift however, resistance is progressively taken out of a parallelresonance circuit compris- 5 ing the primary of an audio frequencytransformer and a condenser of desired capacity so that the lowfrequencies are augmented simultaneously with the attenuation of thehigh frequencies. 10

This is accomplished by inexpensive mechanism which comprises only apotentiometer and two fixed capacities; and with this explanation mydrawing will be clear. I have shown at I an audio frequency tube, theplate 2 of which feeds 15 the primary 3 of an audio frequencytransformer indicated generally at 4. The secondary 5 of thistransformer feeds the grid 6 of a succeeding audio frequency tube 1. Theplate 8 of this tube is connected through a fixed capacity 9, to one 20end of the resistance element of a potentiometer Ill. The plate 2 of,the tube l is connected through the fixed capacity H to the arm orvariable contact point l2 of the potentiometer Ill. The other end of theresistance element of the 5 potentiometer is'connected by a lead I 3 tothe grounded side of the primary of the transformer 4.

When the contact arm I2 is in the extreme left hand position in thefigure, the condenser II will 30 in effect be connected in parallelacross the primary of the transformer 4 resonating it at some lowfrequency range, thus accentuating the low notes. As the arm I2 is movedtoward the right in the figure, more and more resistance is inserted 35into this resonant circuit. At the same time however, resistance isremoved progressively from a feed back circuit connection between theplate 8 of tube 1 and the primary 3 of transformer 4. This feed backconnection comprises 40 1 in series the capacities 9 and H, and it willbe noted that the connection is such that energy is fed back in properphase relationship for regeneration.

The values of capacities 9 and II and of the 45 resistance of thepotentiometer it! may be readily selected. for a desired tone controlwith reference to the other constants of the set. Tone control is, asexplained, achieved by the operator merely by movement of thepotentiometer arm. The change in response is gradual, and any compromisemay be reached between the two extremes. Of course the regenerativecircuit may be caused to respond to low frequencies and the resonancecircuit to high frequencies, if desired. 5

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent, is:

1. In a radio set an audio frequency tube and circuit means connectingthe plate of said tube with the primary of a preceding audio frequencytransformer in proper phase for regeneration, a circuit comprising acondenser paralleled across the primary of an audio frequencytransformer preceding said tube, and controllable means for introducingresistance in inverse proportion into the two circuits.

2. In a radio set a tone control comprising an audio frequency tube, aconnection comprising a capacity between said tube and the primary of apreceding audio frequency transformer, a connection comprising acapacity paralleled across said primary, and means for varying theresponse effects of the resonance and regeneration circuits formed bysaid connections, said means comprising a potentiometer common to bothcircuits.

3. In a radio set a tone control comprising in combination with an audiotube, and a preceding audio transformer, a potentiometer, a leadcomprising a capacity connecting one end of the resistance element ofsaid potentiometer to the plate of said tube, a lead connecting theother end of said resistance-element to the grounded.

side of the primary of said transformer, and a connection including acapacity between the variable arm of said potentiometer and theungrounded side of said transformer.

4. In a radio set a tone control comprising in combination with an audiofrequency tube and a preceding audio frequency transformer, apotentiometer, a connection including a fixed capacity between saidpotentiometer and the plate of said tube, a connection including a fixedcapacity between said potentiometer and the primary of said transformer,said connections effecting a feedback circuit for energy in proper phasefor regeneration, said circuit including both said capacities, and aconnection between said potentiometer 20 LOUIS F. WILLGING.

